Induction-coil.



R. VARLEY. INDUCTION GIL.

APPLxoATIon4 PILBD una, 190s.

986,033. y Patented Man?, 1911.

2 SHEETS-BHEBT 1.

EFFICIENCY CORE REA EFFICIENCY `R. VARLEY'.

INDUCTION COIL.

Prummel FILED uns, leef Patented Mar.7,1911.`

2 BHEETS-SHEET'Z.

UNITED STATES PATENT, oFFicEff L RICHARD VABLEY, or nncmiwoon, New Jnnsny, Assicinon 'ro THE' comunica CORPORATION yor NEW JERSEY.

AUTQCOIL INnUc'rIoN-con..

Englewood, in the county of Bergen and State of New Jersey, have invented certain; new and useful Im rovementsinInduction-- Coils, of which the ollowing is' a full, clear, and exact description. y i;

'lliisA invention relates to inductlon coils for explosion engines, being an exposition4 of the manner in which a coil can be con,

structcd to obtain, so fai' as l ain aware, the maximum or highest possible eiciency in this particular use.

An induction coil as used with an explo-h,

sion engine, is merely an appliance for producing sparks at the i'ate of say, oneor two linndred per second through compressed gases at say one hundred pounds pressure, employing a source of current having about six `volts E. M. I". and a working current consumption of not over one or one and a lia-lf aiiiperes. 'lhesc factors are fixed by the, following considerations. 'lhe number of sparks per second is tixed by the factI that a n'iultziple cylinde qnii'es a coil having a trembler capable of repeated actuations through about 10 angular movements of the engine shaft. 'llie pressure referred to istixed by the compression of present exlilosion engines. The voltage referred to is {ixed partly-by the type ot' three. cell storage battery which is imi-` vcrsrilly marketed for ignition purposes, and partly by thc fact that a higher E.v M. F. craters platinum contacts, and cannotV be practically used. 'llie vcurrent consumption is fixed by the cratcring ditlieult-y mentioned and by the standards now attained with iuduction coils, which have achieved so high'- an efficiency thatI reliable'ignition can be had with a mean average current consumption of 3/4 of an ampere. This being. actually attained in present. practice, it is clear that. any very much higher current consumption would not be tolerated inthe present development of the art. The foregoing results being now practically attained, improvement evii'lently-lies' in still .further re ducing the current consumption thus avoid-A ing cratering. and improving-the economy of operation of the coil.

It is the purpose of my present.y invention to obtain allthese results. i

Inorder to make clear the principles onl Specification of Letters Patent. Application tiled ily 8, `1909. Serial No. 494;

. feet manner.

high speed engine re' which an ideal coil Y v may be constructed yby anyone' skilled inthe art, it issnecessaryto analyze in detail the various phenomena which take place in an induction coil., together with some equations showing .the` inter-relation controlling factors. i

I will first consider the action of an induction.' coil separately from its trembler, that is to say, the working of the coil if the trembler were separatelyactuated in a per- Assuming that a coil has a, core of certain .size and a. primary winding of a certain resistance and number of turns, it is evident that an F. M. F. of six volts acting for an interval of 1 100 of ay second, creates a certa-in tiux or field of magnetic force. The self induction of the primary .winding is expressed hy the formula 41rS z 'gnition purposes of the vvarious ratenteaiaar. 7, 191'1. l

is dependent. upon thel reluctance as shown v in the foregoing equation. ln other words, increasing the cross section Y,of the core lia-s a certain disadvantageous eilect. ()n the other hand`A it has an advantageous effect, since the less the reluctance, the.V greater thc tlux, assuming that the iiiductancc is constantalculation, borne outby practical experiments, proves that increasing thel size of the core increases the field or ilux up to a. certain limit. after which a further iiicrase results in diminishing the field or tlux (for a given limited time constant t). The saine thing for analogous reasons is true of the number of pi'iiiia ry turns S.. It is therefore obvious that for a given E. M. I". and time I. there is theoretically a best size of core and a bestI number of primary turns. Now the trembler oi' vibrator has requirements of its own which may be briefly .summed up as first. making a goodV Contact., second. getting an abrupt and positive sep# aration from the contact. and third, effecting a quick return to the contact.. Allthesc can be obtained b v securing two factors in the induction coil core. namely, suiicicntly strong magnetization, and sucient-ly abrupt change of lmagnetization. Now the best proportions of core and primary winding to secure a flux .or field as first described, are not the best proportions to secure the best action of the trembler' as last described. Experiment and practice has effected what has appeared to be the most desirable combination or compromise. The coils now in use seem to be the best combination or compromise because if the size of the core is either increased or reduced or the number of primary turns is either increased or reduced, a loss of efficiency is felt. For example, increasing the number of primary turns or the size of the magnet core, makes the trembler action better, but the better trembler action is more than offset by the loss of coil efficiency due to the considerations first above mentioned in regard to the flux or fiefd. In order to avoid too complicated mathematics, I will analyze the various effects of alteringthe proportions of the coil by means of graphical curves.

Figure l shows the effect of increasing t-he diameter of the core. the number of turns re- L maining a constant medium value.

The ordinates denote what I term-fluxing efficiency, or in other words flux or field produced by a given E. M. F. (6 volts) in a `given time interval (1,/100second) as above described. The abscissas indicate core areas. il will be seen that the fiuxing efficienc is a maximum at a certain core area and fa ls off when said area is either reduced or increased.

Fig. 2 is a curve showing the effect of changing the number of primary turns', the cross: section remaining a constant medium value. It will be lseen that the efficiency is best when there is a. certain best number of turns, the efficiency diminishing either when the number -is increased or reduced therefrom.

Fig. 3 shows the effect of loading the primary with inductance, such as an exterior coil.

Fig. t is a section of a coil constructed in accordance with the. principles of my invention; and

Fig. 5 is .-1 diagrammatic representation ofI the winding on such ccil.

In Fig. 3 the ordinates indicate efficiency, as before, and the abseissas designate increased inductances duc either to increasing the core area or increasing the number of turns. A l); indicates in a general way the increase of field or flux which would result from increasing either the core area or the innnber of primary turns, were it not for the counter or negative effects of the inductance. The flux or field increase is directly proportionate to the core area, or. to the number of turns; and, as is wellA known, the reluctance almost exactlyinversely proportionate to the core areasin astraight bar magnet; A-C shows the negative o r counter effect due to the inductance; and A-D is the resultant obtained by combining curves -B and A-Q in other words subtracting curve A-C fromA curve A-B. This curve, of course, corresponds to those of Figs. 1 and 2.` It is clear that there is a maximum efficiency point corresponding to the summit of this curve. l E-F,1s a line indicating the effect of an increased number of turns in the primary circuit but assumed to be located entirely outside the coil; in other words loading the coil with an exterior inductance. E-G, shows the effect of loadingv the primary winding with turns which are ineffciently positioned thereon, for example, near one of the poles. This line E-G, evidently will lie between A-B and E-F. The more efficiently located the extra windings are, the more nearly the line E-G will approach A-B in direction. The effect of combining any of the curves A, E, (fr with the curve A-C, is illustrated by the lines E- i', l2 (i2 etc. The points 4G G?, ctc., denote the efficiencies'secured by loading different primary windings with a given extra inductance located near a pole of the primary core. lt will be noted that the most left hand point, G', corresponds to a. higher efficiency than any of the other oints G2', G, etc. But thisl curve, denoted A for convenience, corresponds to adding a fixed number of turns to a primary win ing having considerably less inductance (say 50% or more) than the apparently ideal value indicated by the summit of the cu'rve A--D.'

The gist of my invention consists in loading the primary winding with a few turns directly at the ole which actuatcs the trembler, the loadlng'being done in accordance with the foregoing curves or princi iles. In other words, I provide a few turns o the primary winding for the direct purpose of operating the trembler, which is obviously attained. The trembler will be found to work with all the desirable characteristics heretofore'referred to, even ifit is placed a-quarter of an inch away from the end of the core. This addition of windings alone, however, would diminish rather, than in crease the efficiency of the induction coil unless done in accordance with the principles above pointed out. This is clear from Fig. 3. The effect of having the trembler work properly is to definitely increase the efficiency of the coil by a certain factor. If the efficiency of the coil is at. the point G of Fig. 3, the change of better or more regular trembler action will be to elevate the efficiency to G. If on the other hand, the coil efficiency is at the point G2, the effect of the better trembler willbe to elevate it to the point G. But Gs is lower than the summit of the curve A--D. In other words the coil efficiency is only made the highest possible maximum provided its core cross section and primary turns are very :trembler pole there are four a inch ofthe length of the coil.

considerably l'reduced before the few' extra` turns at the pole are added. b

To illustrate' the foregoin I have shown in Fig. 4 la coil4 which wil drive sparks through a 200 4pound pressure at highest engine speeds and with a six volt battery. The coil has a core denoted 1, 5 3/8 inches long and 1/2 inch in diameter, as a ainst 11/16 or 3/4 of an inch hitherto foun best. The primary denoted 2, consists of -two layers of No. wire, and directl at the ditional layers denoted 3, extending along one-half an It /will beobserved that this is very considerably less than the amount4 of primary windings usually sup lied and corresponding to the summlt of t e curve A-,D. The secondary consists of the usual bobbins of fine wire 4 as can be eilciently cut bythe lines-of force, one terminal of the A' secondary being designated 5, and the other mary matically, the secondar .relatio body proper of said p one po 6, the latter preferably having the usual connection with the primary coil supply Wire .7. .The other primary supply wire 8 1s electrically connected to the trembler stud 9. Fig. 5 diagrammatically illustrates the the body or main portion of the primary coil 7 and the preferably superposedA and Ahence greater didisposed upon said body at the trembler` end thereof.

In 4considering the reactance effect mathesmallextent iniuence t e action of the priand hence there will be considerable complication in the equations involved. For this reason it has been deemed expedient t employ aphics, which serve to show the as being relatively unimportant.

What I claim is:

.1. An induction coil comprising a core and primary and secondary windings, said primary winding having a distinct group of additional turns or' layers disposed upon the rimary winding at e of the coil,'sa1d I group being in seat one end thereof than at the other,

winding will to a' 1p and effect of the windings, theaction 4of the secondary being disregarded riels with the coil and a trembler at such p02. In an induction coil, a magnetizable core, a rality o turns of an electrical conductor, connected in series, said coilhaving a greater number of turns per unit of length of coran a trembler at said first mentioned end.

3. In an induction coil, a magnetizable core, a primary coil proper mounted thereupon, said coil having a greater number of turns per unit of length of core at one end thereof than at the other, said coil;,being disposed along substantially Ithe entire length of said core and having the turns thereof electrically connected in series, and a trembler at said iirst mentioned end.

4. .In an induction coil, amagnetizable core, aprimary coil proper mounted thereupon, said coil having a greater number of turns per unit of length of core at one end thereof than at the other, said coil being disposed along substantially the entire length 4of said -core and having the turns thereof electrically connected in series, the said end of the coil having the greater number of turns per unit of length, comprising turns `of greater diameter than any elsewhere disposed along the core, and a trembler at such end. v

5. An inductioncoil comprisin a core and a primary and secondary win ing, said primary winding being disposed substantially uniformly along the length of said core but having a distinct grou of additional turns or layers superposed) upon the body of said primary Winding at oneend thereof adjacent ay pole of the coil, said additional turns projectin laterally from the said. body and bemg e ectrically connected rimary coil consisting of` a pluin series therewith, and a trembler at such 'f 

